1. Technical Field
The present invention relates to an axle and, more particularly, to a two piece forged axle for use as axle shafts for vehicles.
2. Discussion
Axles generally include a one-piece flange and a shaft section wherein the shaft section has a first end integral with the flange and a second free end having a reduced diameter. In operation, a pair of axles are mechanically coupled for rotation with or relative to one another in a manner known in the art. The current method of producing axles involves hot forging a single piece of stock on equipment commonly known as an upsetter to form a flange section on one end of the stock. The flange section diameter and thickness are limited by the upsetter operation and the starting barstock size necessary to gather this volume in the number of blows the machine can perform on the part. These concerns force the selection of an initial diameter that is significantly larger than the smaller design diameters on the free end of the final shaft section. As a result, the hot forging of the flange section is followed by an expensive process of cold extrusion during which the diameter of the shaft is reduced in a step-wise fashion. Cold extrusion requires the application of a cold extrusion lubricant, usually an expensive phosphate and soap process. Beyond the expenses associated with the multiple step cold extrusion, another drawback of the current axle forming technique includes the mismatch and flashline produced along the sides of the flange from the split die design of upsetters.
The present invention separates the shaft section from the flange section of the axle component to allow for more optimum and independent design and processing of each section. The flange section is produced on vertical forging equipment with more optimized upset ratios, greater design flexibility, and tighter tolerances than are possible on an upsetter. The shaft section, depending on the customer's final design, can vary from a straight piece of barstock to a complex geometry not possible with the current hot upset/cold extrusion process. A further advantage provided by the present invention is that different materials may be selected for the shaft and flange sections whereupon the two parts are forged together into a single axle component. More particularly, the flange is produced with a single or double taper of either straight or compound design that includes a positive mechanical drive interlock such as a spline on its inner diameter. The independently designed shaft section is then inserted into a bore in the flange and the shaft is coupled to the flange by cold, warm, or hot forging.